This is a tooltip text for the decor overlay. You should report that as a bug, because as you saw the descriptions are mixed up. TOOLTIPS.LOWDECOR has a description for high decor areas, and TOOLTIPS.HIGHDECOR shows the low decor headline.

So, there's two ways to get the game to load your strings:
a) Place the strings.po file in the folder I mentioned. The game loads your translations when restarting, the options menu will be empty
b) Use steam workshop, subscribe, and then select in main menu (after some loading)
Since steam workshop is additional error potential, just try and place a strings.po file manually in the folder I listed. A string_template.pot file should already be there. For the fastest test, just replace the big intro text message with something, and you will immediately see if it worked.

Translations only need the strings.po file, you can delete everything else.
If you want to skip any workshop problems (sometimes it loads a little too long on the main menu), just place your strings.po next to the strings_template.pot file in the game directory at OxygenNotIncluded_Data/StreamingAssets/Mods. If the game still doesn't load your translations then, something is wrong with the po file you created.